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How Schizophrenia Impacts Cognitive Function

Cognitive deficits in schizophrenia interfere with real-world functioning.

Schizophrenia is a disorder with readily observable symptoms including hallucinations, delusions, social withdrawal, apathy, and disorganized thinking and behavior. It is also associated with substantial cognitive deficits, which interfere dramatically with everyday functioning. Robert McCutcheon, Richard Keefe, and Philip McGuire recently published an excellent review in the journal Molecular Psychiatry that summarizes current knowledge about cognitive impairment in persons with schizophrenia.
Cognitive deficits associated with schizophrenia include difficulties with attention, working memory, learning, and processing speed. These deficits interfere with real-world functioning. They are associated with increased hospitalization, longer hospital stays, and decreased compliance with treatment.
Cognitive impairment is also a major contributor to illness-related disability, defined as an inability to work productively and/or live independently. Psychiatric illnesses, including schizophrenia, are among the leading causes of disability across the human lifespan.
Although, in general, persons with schizophrenia perform poorly on cognitive tasks and average in the lowest 5 to 10 percent of the population when compared to those without schizophrenia, the degree of deficit varies greatly among individuals. It is possible that some individuals have cognitive deficits in one area while others have deficits in other cognitive domains. Sorting out various patterns of cognitive deficits among individuals will require further research.

Natural History
Cognitive deficits typically precede the onset of behavioral symptoms in individuals who eventually develop schizophrenia. These cognitive deficits are often present during childhood and increase during adolescence. This differs from the time course of cognitive changes in bipolar disorder where such changes occur largely after the onset of mood symptoms.
The cognitive deficits that develop during childhood in those with schizophrenia remain relatively stable through middle adulthood. As individuals become elderly, they are at higher risk for cognitive decline. However, such late-in-life deterioration might result from a variety of health factors that are common in individuals with schizophrenia and that contribute to premature death in these individuals.

Various brain circuits and neurotransmitters play a role in the development of cognitive deficits. Elucidating which neurotransmitter systems are involved in which brain systems will require much more research.

It is well known that both older- and newer-generation antipsychotic drugs do not substantially alter the cognitive deficits associated with schizophrenia. Novel medications are being developed to treat schizophrenia, and increased attention is being directed toward developing drugs that help ameliorate cognitive deficits.
Knowing which specific cognitive deficits an individual with schizophrenia is experiencing can assist caregivers in tailoring psychosocial management. Neuropsychological testing can determine the type and degree of such deficits.
Advances in neuroscience will result in an improved understanding of the nature and causes of schizophrenia. This should lead to advances in novel drug development. Together with increased attention to psychosocial interventions, these advances should aid the development of integrated, personalized treatment approaches to improve the everyday functioning and life satisfaction of those suffering from this devastating psychiatric disorder.

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Schizophrenia and Brain Asymmetry: New Insights

New large-scale study shows alterations in language areas in schizophrenia.

Schizophrenia is a devastating mental health issue that affects about 1% of Americans. Its symptoms can be quite different from patient to patient. Common symptoms include hearing voices and other forms of hallucinations, delusions, paranoia, as well as problems with thinking, and incoherent speech. All these symptoms represent issues with brain functions such as speaking or thinking. Therefore, scientists have conducted many studies looking for changes in the structure of the brains of patients with schizophrenia compared to healthy volunteers, as this may be helpful in understanding the reasons for schizophrenia and potentially creating new ideas for better treatments.
One leading theory suggests that schizophrenia is related to a reduction of so-called hemispheric asymmetries in the language system. In almost all people, brain networks on the left side of the brain are controlling language. In schizophrenia, this leftward asymmetry may be reduced, which may be related to common language issues in patients, such as hearing voices that are not really there. While this is an intriguing theory, previous research studies have yielded very inconsistent results, possibly because the number of people tested in most studies was rather low.
A new study on brain asymmetries and schizophrenia
A new study by the ENIGMA consortium, now published in the journal PNAS, tackled this problem by conducting the largest-ever study on brain asymmetries in schizophrenia (Schijven et al., 2023). The international research team analyzed magnetic resonance imaging data from 5,080 patients with schizophrenia and 6,015 controls. Magnetic resonance imaging is a neuroimaging technique that uses magnets to create high-resolution pictures of the brain. It is commonly used in hospitals for diagnosing different disorders, such as tumors in the brain. In addition to that, it is commonly used in psychological and neuroscientific research in order to assess the brain structure of patients and healthy people.
The scientists compared asymmetries in the thickness of the cortex of the brain between patients with schizophrenia and controls. They found asymmetry differences between the two groups in two brain areas: the rostral anterior cingulate (a brain area related to emotion and cognitive control) and the middle temporal gyrus (a key area for language). Both effects were caused by a thinner cortex on the left side of the brain in patients with schizophrenia compared to controls. This finding is in line with idea that language lateralization is altered in schizophrenia as these changes in the structure of speech area may cause altered function of the speech network.
A further whole-brain analysis of asymmetries revealed that all together, 7% of the variation in brain asymmetries was associated with the status of the participants (schizophrenia patients or control). This suggests broader changes in asymmetries across the brain in schizophrenia that are not limited to language regions. Taken together, the findings of the study show how large-scale neuroscientific studies in patients with mental disorders can be very informative in understanding the potential reasons why patients experience certain symptoms. Further analyzing the brain regions identified in the study using modern neuroscientific and molecular methods may be helpful in understanding the mechanisms behind schizophrenia and finally creating better treatments for patients suffering from this agonizing disorder.

psychology today